1. Field of the Invention
The present invention relates to a compound useful as a monomer for a polymer, for example, for a base resin of a chemically amplified resist composition suitable for an ultra-fine processing technology, a polymer which contains the compound as a monomer, and a resist composition which contains the polymer as a base resin, and a patterning process using the resist composition.
2. Description of the Related Art
It has been needed to make a pattern rule fine with a tendency of high integration and high-speed of LSI in recent years, and a far-ultraviolet-ray lithography is considered as excellent as an ultra-fine processing technology of the next generation. Among them, realization of photolithography using KrF excimer laser light, ArF excimer laser light, and F2 excimer-laser light as a light source has been desired earnestly as technology indispensable to micro-processing of 0.3 μm or less.
For the resist composition for KrF excimer laser, a polyhydroxy styrene having both transparency and etching resistance which are in a usable level is a standard base resin on the fact (see, for example, Japanese Patent Publication No. 2-27660).
On the other hand, for the resist composition for ArF excimer lasers, there have been examined as a base resin a derivative of a polyacrylic acid or a polymethacrylic acid, a polymer which contains a cycloaliphatic compound in a backbone chain (see, for example, Japanese Patent Application Laid-open (KOKAI) No. 9-73173, and Japanese Patent Application Laid-open (KOKAI) No. 10-10739). However, there are both advantages and disadvantages in any of them, and a standard base resin has not yet been decided.
That is, there is an advantage such as a high reactivity of an acidolysis group and high adhesion property with substrate in the case of the resist composition using a derivative of a polyacrylic acid or a polymethacrylic acid, and a comparatively good result is obtained thereby as for sensitivity and a resolution power. However, etching resistance thereof is very low and is not practical, since a backbone chain of the resin is weak. On the other hand, in the case of the resist composition using a polymer which contains a cycloaliphatic compound in a backbone chain, although etching resistance is in a level of practical use, since the backbone chain of the resin is sufficiently strong, sensitivity and resolving power is low, since the reactivity of an acidolysis protective group is significantly inferior compared with those of (meth)acrylics. Furthermore, since the backbone chain of the resin is too strong, an adhesion property with a substrate is low, and it is not suitable either.
Moreover, there is collapse of a pattern due to swelling of a resist film as a common problem to both (meth) acrylic resins and the resin with a cycloaliphatic backbone chain. The resolving power of these kinds of the resist composition has been improved by making a difference in a resolution power before and after exposure large, and therefore, it is very hydrophobic. In the case of the resist composition with a highly hydrophobic property, a film is strongly kept in a non-exposed part and a film is dissolved immediately in an over-exposed part. However, in a quite large exposure area between them, it cannot be dissolved, but is swollen, even though a developer permeates therein. In a very detailed pattern size for which an ArF excimer laser is actually used, the resist composition in which the adjacent patterns are adhered by swelling and collapse cannot be used. With a need for a finer pattern rule, there has been needed a resist composition wherein sensitivity, resolving power, etching resistance, and an adhesion property with a substrate are excellent, and swelling is fully suppressed.